Disorder effects at low temperatures in La_{0.7-x}Y_{x}Ca_{0.3}MnO_{3} manganites

With the aim of probing the effect of magnetic disorder in the low-temperature excitations of manganites, specific-heat measurements were performed in zero field, and in magnetic fields up to 9 T in polycrystalline samples of La_{0.7-x}Y_{x}Ca_{0.3}MnO_{3}, with Y concentrations x=0, 0.10, and 0.15. Yttrium doping yielded the appearance of a cluster-glass state, giving rise to unusual low-temperature behavior of the specific-heat. The main feature observed in the results is a strong enhancement of the specific-heat linear term, which is interpreted as a direct consequence of magnetic disorder. The analysis was further corroborated by resistivity measurements in the same compounds.Comment: 9 pages, 2 figure

Two pairs of proven monozygotic twins discordant for familial amyloid neuropathy (FAP) TTR Met 30.

J Med Genet. 1999 Aug;36(8):629-32. Two pairs of proven monozygotic twins discordant for familial amyloid neuropathy (FAP) TTR Met 30. Munar-Qués M, Pedrosa JL, Coelho T, Gusmão L, Seruca R, Amorim A, Sequeiros J. Grupo de Estudio de la PAF, Palma de Mallorca, Spain. Abstract Twin studies are an important tool in medical genetics for the evaluation of the relative roles of genetic and non-genetic factors in several diseases. Familial amyloidotic polyneuropathy type I (FAP-I), TTR Met 30, was present in two sets of proven monozygotic (MZ) twins, one from Majorca and the other from Portugal. Monozygosity was established by analysis of DNA polymorphisms. Both pairs were discordant for age at onset and some clinical manifestations of FAP-I. We reviewed the differences in age at onset and clinical features in both sets and in two other pairs of presumed MZ twins with FAP-I and compared them with those in MZ twin pairs with other Mendelian disorders, such as neurofibromatosis type 1, Huntington's disease, facioscapulohumeral muscular dystrophy, and myotonic dystrophy. We conclude that, in addition to the postulated modifying genes, there must be a significant contribution from non-genetic factors to the phenotypic variability of FAP-I (age at onset and clinical expression), either because of environmental differences or stochastic events during (or after) the twinning process. PMID: 10465115 [PubMed - indexed for MEDLINE]PMCID: PMC176297

Comparação de acessos do gênero Paspalum quanto ao nível de antibiose à cigarrinha-das-pastagens Notozulia entreriana (Hemiptera: Cercopidae).

As cigarrinhas são pragas importantes e de ocorrência generalizada no Brasil. O uso de gramíneas resistentes é uma alternativa de controle que apresenta grande potencial. No presente ensaio, comparou-se 25 acessos do gênero Paspalum quanto ao nível de antibiose à cigarrinha Notozulia entreriana. Trata-se de acessos de espécies nativas de Paspalum como fonte de cultivares para fins paisagísticos e de recobrimento de superfícies de solo. O ensaio foi conduzido em casa de vegetação. As plantas foram estabelecidas a partir de mudas em pequenos copos plásticos e, posteriormente, transferidas para vasos maiores. Cada vaso foi individualmente coberto com tampa de alumínio possuindo orifício central, para a saída das planta